A first conventional electric warmer disclosed in a Taiwan patent of No. 551482, includes a housing, an electrical heating tube, two fixing units, two inserting cylinders and two springs. The fixing units consists of a front one and rear one, and the rear fixing unit has a fixing member extending to one side, and the front fixing unit has an inverted -shaped sealing surface in its front section, and a hole bored in the sealing surface. Then the sealing surface and the rear fixing unit have a round hole in an upper flat surface for one insert cylinder to fit therein. Each insert cylinder has a groove respectively in an upper and a lower portion of its outer wall, and a groove in an inner wall. Each spring has a large diameter in an upper portion and a small diameter in a lower portion, and the large upper portion can fit in the groove of the inner wall and is fixed in the insert cylinder, and the small lower portion supports the electric heating tube to let it not fall down. The electric heating tube is inserted in the spring fixed in the insert cylinder, supported by the small diameter portion. Then the insert cylinder together with the electric heating tube and the spring is inserted in the round hole and the square hole of the fixing units, with the grooves of the outer wall of the insert cylinder fit with the round hole and the square hole of the fixing units. Then the fixing units are fixed in the housing of the warmer.
The first conventional electric warmer just described, having an electric heating tube made of quartz, has a disadvantage that the heating coefficient of the quartz heating tube is high and its temperature is not easy to control.
A second conventional electric warmer using infrared ray disclosed in Taiwan patent of No. 470155 includes a body and a heating element arranged in the body, and a decorative net plate combined with the front side of the body, which is formed with thin plates surrounding a hollow interior, plural fixing bases provided in the interior for combining electric heating plates coated with electrical heating films connected with a switch on a side of the body by conductive terminals and wires. Then the switch can control the heating plates. The electrically heating plates are not only kept stably by the fixing units but also by a special sloped surface of a press plate respectively fixed with bolts in two sides of the body.
A third conventional convectional radial electric warmer disclosed in a China patent of No. CN 1401941A includes an electric heating plate fixed stably by a frame, two sides plates and two lateral rods, an upper housing, a left housing and a right housing and a metal net combined together. The electric heating plate has electric heating films, which is formed with many kinds of inorganic oxides formed on an electrical insulating base by means of chemical evaporation and sediment process. This third conventional electric warmer is costly, requiring complicated processes.